64 research outputs found
Modulation of functional pendant chains within poly(ethylene glycol) hydrogels for refined control of protein release
Hydrogels are highly attractive delivery vehicles for therapeutic proteins. Their innate biocompatibility, hydrophilicity and aqueous permeability allow stable encapsulation and release of proteins. The release rates also can be controlled simply by altering the crosslinking density of the polymeric network. However, the crosslinking density also influences the mechanical properties of hydrogels, generally opposite to the permeability. In addition, the release of larger proteins may be hindered below critically diminished porosity determined by the crosslinking density. Herein, the physical properties of the hydrogels are tuned by presenting functional pendant chains, independent of crosslinking density. Heterobifunctional poly(ethylene glycol) monomethacrylate (PEGMA) with various end functional groups is synthesized and copolymerized with PEG dimethacrylate (PEGDA) to engineer PEG hydrogels with pendant PEG chains. The pendant chains of the PEG hydrogels consisting of sulfonate, trimethylammonium chloride, and phenyl groups are utilized to provide negative charge, positive charge and hydrophobicity, respectively, to the hydrogels. The release rates of proteins with different isoelectric points are controlled in a wide range by the type and the density of functional pendant chains via electrostatic and hydrophobic interactions
Stochastic backgrounds of relic gravitons: a theoretical appraisal
Stochastic backgrounds or relic gravitons, if ever detected, will constitute
a prima facie evidence of physical processes taking place during the earliest
stages of the evolution of the plasma. The essentials of the stochastic
backgrounds of relic gravitons are hereby introduced and reviewed. The pivotal
observables customarily employed to infer the properties of the relic gravitons
are discussed both in the framework of the CDM paradigm as well as in
neighboring contexts. The complementarity between experiments measuring the
polarization of the Cosmic Microwave Background (such as, for instance, WMAP,
Capmap, Quad, Cbi, just to mention a few) and wide band interferometers (e.g.
Virgo, Ligo, Geo, Tama) is emphasized. While the analysis of the microwave sky
strongly constrains the low-frequency tail of the relic graviton spectrum,
wide-band detectors are sensitive to much higher frequencies where the spectral
energy density depends chiefly upon the (poorly known) rate of
post-inflationary expansion.Comment: 94 pages, 32 figure
Graft healing in anterior cruciate ligament reconstruction
Successful anterior cruciate ligament reconstruction with a tendon graft necessitates solid healing of the tendon graft in the bone tunnel. Improvement of graft healing to bone is crucial for facilitating an early and aggressive rehabilitation and ensuring rapid return to pre-injury levels activity. Tendon graft healing in a bone tunnel requires bone ingrowth into the tendon. Indirect Sharpey fiber formation and direct fibrocartilage fixation confer different anchorage strength and interface properties at the tendon-bone interface. For enhancing tendon graft-to-bone healing, we introduce a strategy that includes the use of periosteum, hydrogel supplemented with periosteal progenitor cells and bone morphogenetic protein-2, and a periosteal progenitor cell sheet. Future studies include the use of cytokines, gene therapy, stem cells, platelet-rich plasma, and mechanical stress for tendon-to-bone healing. These strategies are currently under investigation, and will be applied in the clinical setting in the near future
Designing Bioactive Delivery Systems for Tissue Regeneration
The direct infusion of macromolecules into defect sites generally does not impart adequate physiological responses. Without the protection of delivery systems, inductive molecules may likely redistribute away from their desired locale and are vulnerable to degradation. In order to achieve efficacy, large doses supplied at interval time periods are necessary, often at great expense and ensuing detrimental side effects. The selection of a delivery system plays an important role in the rate of re-growth and functionality of regenerating tissue: not only do the release kinetics of inductive molecules and their consequent bioactivities need to be considered, but also how the delivery system interacts and integrates with its surrounding host environment. In the current review, we describe the means of release of macromolecules from hydrogels, polymeric microspheres, and porous scaffolds along with the selection and utilization of bioactive delivery systems in a variety of tissue-engineering strategies
All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run
We present results from a search for gravitational-wave bursts in the data
collected by the LIGO and Virgo detectors between July 7, 2009 and October 20,
2010: data are analyzed when at least two of the three LIGO-Virgo detectors are
in coincident operation, with a total observation time of 207 days. The
analysis searches for transients of duration < 1 s over the frequency band
64-5000 Hz, without other assumptions on the signal waveform, polarization,
direction or occurrence time. All identified events are consistent with the
expected accidental background. We set frequentist upper limits on the rate of
gravitational-wave bursts by combining this search with the previous LIGO-Virgo
search on the data collected between November 2005 and October 2007. The upper
limit on the rate of strong gravitational-wave bursts at the Earth is 1.3
events per year at 90% confidence. We also present upper limits on source rate
density per year and Mpc^3 for sample populations of standard-candle sources.
As in the previous joint run, typical sensitivities of the search in terms of
the root-sum-squared strain amplitude for these waveforms lie in the range 5
10^-22 Hz^-1/2 to 1 10^-20 Hz^-1/2. The combination of the two joint runs
entails the most sensitive all-sky search for generic gravitational-wave bursts
and synthesizes the results achieved by the initial generation of
interferometric detectors.Comment: 15 pages, 7 figures: data for plots and archived public version at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=70814&version=19, see
also the public announcement at
http://www.ligo.org/science/Publication-S6BurstAllSky
Reconnaissance-Scale Prospectivity Analysis for Gold Mineralisation in the Southern Uplands-Down-Longford Terrane, Northern Ireland
In vivo biocompatibility of two PEG/PAA interpenetrating polymer networks as corneal inlays following deep stromal pocket implantation
Observation of Gravitational Waves from a Binary Black Hole Merger
On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave
Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in
frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21. It matches the waveform
predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the
resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a
false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater
than 5.1σ. The source lies at a luminosity distance of 410þ160
−180 Mpc corresponding to a redshift z ¼ 0.09þ0.03 −0.04 .
In the source frame, the initial black hole masses are 36þ5
−4M⊙ and 29þ4
−4M⊙, and the final black hole mass is
62þ4
−4M⊙, with 3.0þ0.5 −0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals.
These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct
detection of gravitational waves and the first observation of a binary black hole merger
Morphological and functional characterization of a pancreatic beta-cell line microencapsulated in sodium cellulose sulfate/poly(diallyldimethylammonium chloride)
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